On-chip embedded memory with non-volatility can enable energy and computational efficiency. Several new types of solid-state, high-density, non-volatile memories store information using a memory element with a variable resistance. The resistance of spin transfer torque-magnetic random access memory (STT-MRAM) depends on the relative magnetization polarities of two magnetic layers. Other variable resistance memories include resistive random access memory (ReRAM) and conductive bridging random access memory (CbRAM), whose resistances depend on the formation and elimination of conduction paths through a dielectric or an electrolyte. There is also phase change memory (PCM), for which the resistivity of a cell depends on the crystalline or amorphous state of a chalcogenide.
For these resistive memories, read operation is generally faster than write operation, and the write current is generally larger than the read current. Unlike static random access memory (SRAM) and dynamic random access memory (DRAM), which consume transient write power, resistive memory still consumes static write power whether or not the cell is flipped during write operation. The read power of these resistive memories may also be static depending on the implementation of the read sensor. Reducing read and write power is a challenge for resistive memory in order to meet the targets for high performance and low power applications.